Process of carbonizing



May 5, 1925. 1,536,696

G. W. WALLACE PROCES 5 OF CARBONI Z ING Filed Sept. 17, 1923 WASHERVVizllace,

(Horns Patented May 5, 1925.

UNITED STATES GEORGE WIGHTHAN WALLACE, 01 SAN FRANCISCO, CALIFORNIA.

PROCESS OF CARBONIZING.

Application filed September 17, 1828. Serial- No. 883,240.

To all whom it may concern:

Be it known that I, GEORGE W. WALLACE, a citizen of the United States,residinga't San Francisco, in the county of San Francisco and State ofCalifornia, have invented certain new and useful Improvements inProcesses of Carbonizing, of which the following is a specification.

This invention relates to processes of carbonizing; and it comprises amethod of carbonizing shale, lignite, coal, etc., to obtain valuablevolatilizable roducts wherein shale, orthe like (usually, ut. notnecessarily, moist or moistened) is carbonized in a vertical columnunder conditions causing a transverse band or zone of carbonization toadvance progressively downward towards and to the colder, moist lowerend, the temperature in this zone being usually around 800 F and the thedownward progression of the zone being efl'ected by a hot down draft ofreturned combustible gases admixed with air; all as more fullyhereinafter set fort-l1 and as claimed.

In distilling shale, lignite, coal, etc., to obtain oils and tars andammonia, the bituminous bodies present break up primarily by an actionanalogous to the charring of wood; an action which, as a whole, if notactually exothermic, at all events requires the addition of very littleforeign heat once the materials are brought to a reacting temperature.The action is the same as that forming the first stage in coking coaland is called carbonization; a term which may be here used. Onceinitiated at any point in a mass of hot fuel, the decomposition reactiontends to' become self-propagating and advance elsewhere. Possibly theactual decomposition itself is always exothermic; but the net result ofthe complex of actions taking place and vaporization of the volatileproducts formed, with consumption of heat. may or may not be aliberation of heat. However, if added heat is required, the amount, inthermal units, is, as noted, usually very little. \Vith various coalsunder various conditions, recorded results vary between a liberation ofabout 780 Brit sh thermal units per pound of coal to an absorption ofabout 170. One of the products of the primary decomposition is alwayscombustible gas (ethylene, ethane, etc.) and if heating conditions benot carefully regulated, the amount of this gas is materially augmentedby secondary decomposition of the oils and tars primarily produced. Thisis of course undesirable, except where gas is the product sought.

It is Well recognized in the art that low tem erature distillation isdesirable in order to o tain a maximum of oils and tars; and manymethods of distilling have been proposed with this end in view. For themost part, however, they have been unsuccessful in securing'the fullresult sought because of the engineering and technical diflicultiesincident to heating any substantial mass of pulverulent or fragmentarynature evenly and to exact temperatures throughout; and particularlywhere, as in the present case, the result is, or may be, aself-propagating exothermic reaction. Ordinarily, moreover, the methodsare, thermally speaking, expensive; they require much heat to be usedand particularly with externally heated retorts; this being especiallytrue Where substantial yields of ammonia aresought and currents of steamare used to assi.-t in its extrication. The question of the heatnecessary is particularly serious in dealing with shales and ligniteshigh in mineral matter, of low fuel value.

It is the object of the present invention to provide a methodparticularly applicable to the treatment of oil shales, but also usefulwith lignites and coals, in order to produce maximum yields of oils andtars, as well as of ammonia, with a minimum consumption of fuel. Thesolid product of the action may be mineral matter or ash, or it may be acarbonized mass of coky or semi-coky nature, having fuel value. In orderto accomplish my end, I take advantage of'the stated selfpropagatingnature of the carbonizing reaction, instituting a carbonizing reactionin the top of a column or body of shale in a suitab e container andeffecting a downward regulated travel of this zone of carbonizingtowards and to the lower end of the column. The carbonizing action is,as stated, usually exothermic, that is, is attended with a localevolution of heat and an increase in temperature. In order to controlthe reaction and its propagation, I balance the heat and volume of adowndraft of burning gases traveling in the direction of propagationagainst the cooling efl'ect of moisture in the line of advance. In sodoing, I am enabled to achieve a new result: rapid carbonization at acontrolled and low temperature. In

practice, above (or in heat communicating.

relationship to) the head of the column of shale I burn gases to producea higher temperature than that required to initiate carbonization, whilethe body of shale is wet or moist to a point just below the temporarylocus of the zone of carbonization, and there fore at a temperature notexceeding 212 F. The exact distance between the moist zone where suddencooling takes place and the advancing high temperature face of thecarbonization zone depends on the volume of hot gases passing, anddrying out the material. The charge is usually in fragments of two inchsize or less, though run of mine may be used and it holds whatever waterwill adhere, the rest draining downward. Hot gases are passed downwardthrough the shale towards the cold end. By regulating the quantity ofgases in the downdraft and their temperature, obviously I can exerciseexact control of the progress of the carbonization zone. It is a matterof balancing the heat and the volume of the gases in the drowndraftagainst the cooling effect of the moisture in the shale below the zone.

Usually some of the combustible gases resulting from the action itselfand collected beyond the condensers (which I may here call tail gases)are returned to a point in the treating apparatus just above 'the massof shale under treatment and are there burnt with air. The amount ofheat developed depends upon the quantity of gas so introduced and burnt.The hot mixed body of gases passing downward through the mas of shalegives the heat necessary to initiate and maintain the carbonization; i.e., the heat required to compensate for radiation, for heating the solidmaterials to a somewhat higher temperature, for vaporization and thelike. The downdraft carries heat, as well as vapors and gases, forwardbeyond the lower advancing face of the zone of carbonization andprcheats the materials to be carbonized. The primary products ofcarbonization are cooled there- 'by. Under the circumstances, theseproducts leave the advancing face really as a sort of fog or fume, welldistributed through the draft current and there is no tendency for theshaleto clog with tar. The zone of preheating bclowthe advancing face ofthe carbonizing zone is limited in its length by the presence 0 liquidwater therebelow. At some point n t far below the advancing face of thecarbonizing zone, which I usually keep at a temperature around 800' F.,the temperature of the shale cannot exceed 212 F. because of evaporatingwater and liquids. Between these points is a preheating and drying zoneof a length depending upon the gas speed. The moisture in the fuel isevaporated in the preheating zone with a corresponding consumption ofheat units;

but these heat units are largely given back to the shale when the watervapor passes downward and is again condensed by the underlying layers ofcool shale. The presence of the water vapor just below the advancingface of the carbonizing zone aids materially in giving high yields ofammonia, and is also advantageous in producing a quick cooling of thevapors leaving the carbonizin face with the downdraft. Oil shalecontaining 15 to 20 per cent of oil or bituminous matter may carry ashigh as 8 to 12 per cent of water and retains a considerable amount of H0 even when passed through a drier or preheater or heat exchanger. Inthe operation of the process as just described, the water naturallypresent in the shale, though not absolutely essential, is definitelyadvantageous, instead of being detrimental. In addition to the water ormoisture in the shale, some H O is formed by the combustion of thereturned tail gases and these gases are usually moist in any event; theyleave the scrubber saturated with water vapor. It is, however, oftenuseful to add some water with material not naturally carrying muchwater. The water in the material, or that added, while vaporizing duringthe process, is largely again liquified; and to this extent thevaporization does not involve any loss of heat units. Using a shalewith, say, 10 per cent of water in it, much of this water is extractedfrom the shale in the present process in the liquid form.

At the base of the column pass away liquid water and liquid oily andtarry products, together with various gases and vapors resulting fromthe operation. Ordinarily, until the carbonizing and preheating zonesapproach the bottom of the column of shale, the temperature at thispoint is around 140-160 F. The gases drawn off at this point are amixture of the hydrocarbon gases produced in carbonization with producergas formed by the action of the air on the carbon, and are saturatedwith water vapor at the temperature obtaining at the base of the column.They carry much oil and water as a fog or fume. water and oils into asettling tank for separation and pass the gases through cooling andscrubbing towers, where there is a further recovery of liquid oils. Thefinal gases may be oil-scrubbed to extract uncondensed vapors. The tailgases, or some portion of them, I may send to storage or return directlyto the head of the column of shale to furnish the heating downdraft.Where there are several units under the present invention in operation,it is convenient to have them out of hase with each other, so that thosefurnishing much gas can supply it to those in which the development ofgas is insufficient. Ordinarily, I find it better, where Ordinarily, Idraw 0s liquid 1 plenty of gases are available, to feed more gas thanair to the head of the column, thereby giving a downdraft of what may becalled a reducin nature; i. e., there is not enough air added to burnall the gas. But, as stated, at some stage of the operation there maynot be suflicient gas to do this and in such event, I use such quantityof air as ma be necessary to furnish heat and volume 0 draft gases. Theair reacts with residual carbon to give producer gas.

While I have stated that the combustion of the gases takes place abovethe head of the column of material, yet actually more or less of thecombustion may take place in the interstices of the top layersby a sortof surface combustion effect. The particular way in which combustion iseffected above the column depends to some extent upon the material.Where the material is a shale high in mineral matter of fusible nature,I prefer not to have the combustion temperature go too high; and wherethe residue left by carbonization contains enough carbon to make itvaluable as fuel, as in treating lignites and coals, I cut down theaccess of an as far as possible to that required for furnishing heat ordraft volume. In either event, the presence of a comparatively largeproportion of unburnt returned combustible gases is advantageous. Underfamiliar equilibrium'principles, the presence of these gases tends torestrain the formatlon of like gases in carbonization. And theyappear toact to shield the oils. Oxidation in the carbonization zone isnot'desirable.

The oils drawn off at the base of the column and those collected in thevarious scrubbing devices are distilled in the usual way to obtaincommercial oils, gasoline, kerosene, lubricating oil, etc.

As the carbonization of the shale is effected in an atmosphere whichcontains water vapor, a large proportion of the nitrogen present in theoriginal material reappears as ammonia-J secure excellent yields ofammonia. This ammonia is recovered from the efliuent water by the usualprocesses.

In the accompanying illustration I have shown, more or lessdiagrammatically, certain apparatus within the purview of my inventionand susceptible of use in performing the described process. This view isin central vertical section, certain parts being shown in elevation. Inthe showing,

Element 1 designates a casing or generator of any suitable material,such as brickwork, iron, etc., provided with charging means 2, grate 3and oil receptacle 4. As shown, the casing is provided at a point abovethe normal level of solid material therein with air inlet 5 and gasinlet 6. At the bottom the casing is tapped by outlet pipe 7 leadinggases and condensed liquids away. The liquids pass to separator .8

shown as rovidedwith internal bafiles where the 011 and water areseparated; each being withdrawn for suitable treatment elsewhere; theoil to be distilled and the water going to an ammonia separator. Thegases in line 7 pass by branch 9 to water cooled condenser 10, wherethere is a separation of further oil and water, which may go back to 8through valved outlet 11, or to similar separating devices. The cooledresidual gases are withdrawn by suction fan 12, which producessuction'on the whole line, and usually sent to a second water cooledcondenser, indicated at 13. Where ammonia is to be recovered, as isgenerally the case, I next pass the gases through one or more ammoniascrubbers of the usual type. One is shown as 14. Ordinarily, I finallypass the gases through an oil scrubber or absorp tion tower 15. Tailgases leave this scrubber through pipe 16, as much as may be wantedbeing returned for the operation through valved pipe 17 forming thecontinuation of inlet 6 previously alluded to. Branch pipe 18 may beprovided leading to gasometer means (not shown) for storage purposes orfor averaging out fluctuations.

In the operation of the described device on oil shale, the generator maybe filled with shale to the normal level marked A, and gas and airsupplied to the top of the casing to produce a hot downdraft under theinfluence of suction from fan 12. They may of course be supplied underpressure, 1f deslred. The hot downdraft of burning gases initiates atransverse zone of carbonizatlon which travels steadily downward. In thedrawing, I have indicated this traveling transverse layer somewhat belowthe top as B. Below is a drying and preheating zone which I haveindicated as C. As the zone of carbonization travels downward, the hotdraft gases passing ahead of it preheat and dry the material in zone C,and pass on into the untreated or cool shale below; this cooler layerbeing indicated as a whole by D. Here the gases drop their moisture, tarand oils, which trickle downward. This action continues until the zoneof carbonization approaches the bottom of the column-zone D alwaysremaining at a temperature somewhere below 212 F. until this time. Whenthe zone of carbonization reaches grate 3, the operation is interruptedand the residual ash or coke (as the case may be) removedin any suitablemanner. In the case of oil shale, the residue is usually of littleheating value, but in treating lignites and the like, it is ofconsiderable fuel value. The present invention is particularlyapplicable to these lignites, since it permits of the removal of much oftheir water in liquid form, i. e., without the consumption of heatincident to drying, or complete drying, in the usual ways.

While I have described the use of combustible gases arising from theoperation itself, they may of course be replaced or supplemented bycombustible gases from other sources, such as natural gas. As acomponent of the downdraft, natural gas, which is largely methane, hassome advantages. The operation as shown and described is discontinuous;successive batches of shale being treated in the generator; butapparatus may be provided enabling the operation to be made continuous.

What I claim is.-

1. In the low temperature carbonization and distillation of shale andthe like, the process of producing a controlled rapid low temperaturecarbonization which comprises initiating, maintaining and controlling adownwardly advancing zone of low temperature carbonization anddistillation in a moist column of material by a downdraft of hot gasestherethrough, said gases comprising returned combustible gases, arisingfromthe operation, burning with admixed air and control of the advanceof the zone being effected by regulation of the amount and proportion ofthe said gases and air.

2. In the low temperature carbonization and distillation of shale andthe like, the process which comprises initiating, maintaining andcontrolling a downwardly advancing zone of low temperature carbonizationand distillation in a moist column of material by a downdraft of hotgases therethrough, said gases comprising returned combustible gasesarising from the operation, burning with admixed air in amountinsufficient for their combustion and control of the advance of the zonebeing effects ed by regulation of the amount and proportion of the saidgases and air.

3. In the low temperature carbonization and distillation of shale andthe like, the

process of producing and maintaining a regulated rapid low temperaturecarbonization and distillation which comprises transmitting downwardlythrough a pervious moist column of shale a burning draft of combustiblegases and air, regulation of the carbonization being effected by controlof the amount and proportions of such gases and air so burning.

4. In the low temperature carbonization and distillation of shale andthe like, the process which comprises transmitting downwardly through apervious moist column of shale a burning draft of combustible gases andair to give an advancing zone of carbonization and distillation; thebottom of the column being maintained at a temperature not above 212 F.until just before the downwardly advancing zone of carbonizationapproaches'it and an intermediate zone of preheating and drying betweenthe advancing faceof the carbonizing zone and the portion of the columnat a temperature not above-212 F. being maintained by suitableadjustment of the air and gases so introduced.

5. The process of carbonizing oil shale or the like in a closed verticalchamber which comprises initiating or setting up a zone of gaseouscombustion above a body of shale in said chamber to initiate andmaintain a zone of carbonization insaid chamber and causing said zone ofcarbonization to progross downwardly through the column or body of shalein said chamber.

6. The process of carbonizing oil shale or the like in a closed verticalchamber which comprises initiating or setting up a zone of gaseouscombustion giving a body of flamin gases of reducing nature, above abody 0t shale in said chamber to initiate and maintain a zone ofcarbonization in said chamber and causing said zone of carbonization toprogress downwardly through 1tohe column or body of shale in saidchamera 7. The process which comprises initiating a zone of gaseouscombustion at the top of a body of shale in a closed chamber, andsetting up a downdraft of the products of said combustion through thebody of shale, whereby a zone of carbonization is caused to progressthrough said body.

8. The process which comprises creating a zone of gaseous combustion byburning a mixture of air and gas in the top of a closed chambercontaining a body of shale, causing the resulting flaming gaseousproducts to pass downwardly through said ,body, drawing off and treatingin the usual way the condensed and uncondensed products 01' distillationfrom the bottom of said chamber, and returning some of the uncondensedgases in the form of combustible gas to the top of said chamber tomaintain said zone of gaseous combustion.

9. The process of extracting oil from shale and the like which consistsin creating a zone of gaseous combustion above a body of shale in aclosed chamber, causing a downward draft of the products of said zone ofcombustion through the body of shale, recovering the distillationproducts from the bottom of said chamber, and returning some of thegaseous products to said zone of combustion therein.

10. In the low temperature distillation and carbonization of shale, theprocess which comprises introducing a burning mixture of combustible gasand air above a vertical pervious column of shale having a moist baseand passing said mixture downwardly therethrough and thereby initiatingand propagating a downwardly moving zone of carbonization anddistillation with a substantial zone of preheating and drying betweensaid carbonization zone and said moist base until just before theadvancing face of the carbonization zone reaches the bottom of thecolumn, the heating action of the burning mixture and its volume beingbalanced against the coonng action of the moisture. and. liquids in theline of propagation to control the progress of the carbonization zoneand to preserve a substantial zone of preheating and drying. 10

In testimony whereof, I have hereunto affixed my signature.

GEORGE WIGHTMAN WALLACE.

